It has been shown in this work that MD combined with GFN2-xTB is an efficient method to produce qualitatively correct mass spectra.
The dissociation mechanisms are accessed by directly extracting MD trajectories and verified by IR calculations and experiments on fragments.
An advantage of this MD approach is that it is capable of probing dissociation events frame by frame.
The fragment comes out in a more natural way than global minimum optimization. MD simulations have shown that the C\(_2\) H\(_4\)  loss is strongly dependent on the geometry of superhydrogenated pyrenes.
Only superhydrogenated pyrenes which have the proton located on the carbon next to the trio group give a significant C\(_2\) H\(_4\)  yield.
Further DFT calculations lead to the conclusion that this geometry requirement is also valid for ethylene formation from other superhydrogenated PAHs.
This work demonstrates the importance of the hydrogenated edges in the production of small hydrocarbons from the processing of superhydrogenated PAHs.
Including this pathway in chemical models may reduce the disagreement between chemical models and observations in estimating the C\(_2\) H\(_4\)  abundance [1]}.
In relation to PAH evolution in space, this study provides more evidence on the weakening of the carbon backbone due to the presence of aliphatic C-H bonds which are also reported in superhydrogenated PAHs [2]} or alkylated PAHs [3]}.

The work is supported by the Danish National Research Foundation through the Center of Excellence “InterCat” (Grant agreement no.: DNRF150) and the European Union (EU) and Horizon 2020 funding award under the Marie Skłodowska-Curie action to the EUROPAH consortium, grant number 722346.
We acknowledge support from VILLUM FONDEN (Investigator grant, Project No. 16562).
